Apparatus for controlling or assisting respiration



Dec. 18, 1962 G. D. BLACK 3,068,857

APPARATUS FOR CONTROLLING OR 'ASSISTING RESPIRATION Filed Nov. 16, 1959 PRESSURE CYCLING UNIT UNIT I Inventor sEoFp-wesy DONALD .eL ck ace/14w Attorney United States Patent Ofiice 3,068,857 Patented Dec. 18, 1962 3,068,857 APPARATUS FGR CONTROLLING OR ASSISTENG RESPRATION Geofirey Donald Black, Tottenham, London, England,

assignor to The British Oxygen Company Limited, a

company of Great Britain Filed Nov. 16, 1959, Ser. No. 853,351 Claims priority, application Great Britain Nov. 19, 1953 1 Claim. (Cl. 128-29) This invention relates to apparatus for controlling or assisting respiration and particularly to such apparatus for use in the administration of anaesthetic gas mixtures in a closed system.

Apparatus of this type includes an expandable reservoir such as a flexible bellows or an inflatable bag which is connected by means of suitable piping to a face piece, endotracheal tube or the like and is adapted to deliver an anaesthetic gas mixture to, and receive exhaled gases from the lungs. Provision is made for the controlled admission of oxygen or anaesthetic gas mixture to the system as required and for the removal of carbon dioxide.

The respiratory movements may be controlled by hand actuation of the reservoir by the anaesthetist but this may be inconvenient and is arduous when artificial respiration has to be applied over a prolonged period. It is also known to surround the reservoir with a rigid airtight vessel to which gas under pressure is intermittently supplied so as rhythmically to compress the reservoir and force the gas mixture contained therein into the lungs. In the periods between these positive pressure pulses, depending upon whether natural or forced exhalation is desired, either the gas in the rigid chamber is released to atmosphere so that the reservoir is expanded under pressure of the gases expelled by elastic recoil of the lungs, or a negative pressure is developed in the chamber so as forcibly to expand the reservoir and suck gas out of the lungs.

It is an object of the invention to provide apparatus for controlling or assisting respiration including novel means for creating a negative pressure in the lungs.

According to the present invention, apparatus for controlling or assisting respiration comprises a closed respiratory system including an expandable reservoir adapted to communicate with the lungs of a patient, a rigid airtight chamber surrounding the reservoir, means for intermittently supplying gas under pressure to the interior of the rigid chamber alternately operable with means for releasing gas therefrom, and loading means associated with the reservoir for causing it to expand when gas is released from the chamber whereby a negative pressure is created in the reservoir.

The reservoir is preferably a flexible bellows fixed at one end, but it may also be in the form of a chamber having one wall formed as a piston or diaphragm. The loading means may consist of a weight attached to the reservoir, that is, for example, to the free end of the bellows. The arrangement is such that, on release of gas from the rigid chamber, the Weight moves under the influence of gravity to expand the bellows. The weight is preferably detachable and provision may be made for securing any one of a range of difierent weights so as to vary the degree of expansion of the bellows, and consequently to vary the negative pressure which can be produced in the lungs. However, substitution of weights cannot be effected Whilst the apparatus is in use, and it may therefore be more convenient to provide independent means for varying the negative pressure.

In accordance with a feature of the invention adjustable means are provided for varying the negative pressure which may produced in the lungs by expansion of the reservoir.

The adjustable means for varying the negative pressure may be a spring-loaded valve located either in the respiratory circuit or in the driving circuit, that is to say, the circuit which includes the rigid chamber. In the former case the arrangement s such that the valve remains closed until the negative pressure developed in the reservoir is sufficient to overcome the pressure exerted by the spring. In the latter case the valve may serve also as the means for releasing gas from the rigid chamber.

Any suitable means such as an injector may be employed for supplying gas under pressure to the interior of the rigid chamber, valve means operated by a pressure responsive member responsive to the pressure in the patients lungs, or a closely related pressure, being provided for cutting off the flow of gas to the injector when the desired positive pressure is produced in the lungs and for restoring the flow of gas to the injector after a predetermined interval. Alternatively the flow of gas to the injector may be restored when the desired negative pressure is produced. In this latter instance the spring loaded valve may be omitted and the adjustable means for varying the negative pressure may then associated with the pressure responsive member. The pressure cycling unit described may be so designed that actuation of the valve means to cut off the flow of gas to the injector also causes the release of gas from the rigid chamber to atmosphere.

Two embodiments of the invention are illustrated diagrammatically in H6. 1 and FIG. 2 of the drawings.

FIG. 1 shows a reservoir 1 in the form of a flexible bellows having connections 2 and 3 leading respectively to and from a patients face mask, endotracheal or tracheotomy tube. A non-return Valve 4 is interposed in the connection 2, and a carbon dioxide absorber 5 and spring-loaded valve 6 are interposed in connection 3. Fresh gas mixture or oxygen is delivered to the bellows 1 as required through a pipe 7. The bellows 1 has a weight 8 secured to its free end and is enclosed in a rigid chamber to which gas under pressure is delivered intermittently through a pipe 10 from a pressure-cycling unit (not shown).

In operation, a predetermined volume of anaesthetic gas mixture is delivered to the bellows 1 through the pipe 7. Driving gas is then admitted to the rigid chamber 9 from the pressure cycling unit to compress the bellows and force the gas mixture into the patients lungs. When the desired pressure is reached the fiow of driving gas is interrupted, the gas contained in the rigid chamber 9 being permitted to escape via the pressure cycling unit to atmosphere. The weight 8 moves under the influence of gravity to expand the bellows 1 and create a negative pressure in the lungs, the value of this negative pressure being determined by the setting of the spring-loaded valve 6. After a predetermined interval the flow of driving gas from the pressure cycling unit is restored.

In the embodiment illustrated in FIG. 2, the reservoir or flexible bellows 13 carrying a weight 14 at its free end is enclosed in a rigid chamber 15 having a connection 16 through which gas under pressure is admitted from a pressure cycling unit (not shown). The interior of the bellows 13 is connected to the patient through a pipe 17 and CO absorber 18. A non-return valve 19 is located in the connection 16 and passages 20 and 21 lead from upstream and downstream of the valve respectively to either side of the diaphragm 22 of a springloaded valve 23'. The valve member 24- is biased towards its seat by an adjustable spring 25. A magnet 26 or toggle spring is also provided to hold the valve member 24 against its seat so as to prevent premature opening of the valve 23 and impart a snap-action thereto.

In operation, the valve 23 serves the same purpose as the valve 6 in the embodiment illustrated in FIG. 1. When gas is being admitted to the rigid chamber 15, the pressures on both sides of the diaphragm 22 are balanced and the valve 23 remains closed, but when the supply of gas is interrupted the pressure transmitted to the diaphragm through the passage 29' is relieved and the valve is opened to permit gas to escape from the chamber 15 until a preset minimum pressure determined by the spring loading i'srached. The valve 23 thus imposes an adjustable amount of back pressure which ofi-sets to any chosen degree the suction elfect of the weight 14 loading the bellows 13. By loading the bellows to produce a negative pressure in excess of that required, it is possible by suitably adjusting the spring loading on the valve 23 to apply and desired negative pressure.

I claim:

Apparatus for controlling or assisting respiration, comprising a closed respiratory system including an expandable reservoir in the form of a flexible bellows, a conduit communicating with the interior of said bellows and with the lungs of a patient, a rigid airtight chamber surrounding said reservoir and fixed to one end of said bellows, a supply conduit, pressure cycling supply means for intermittently supplying gas under pressure to the interior of the rigid chamber via said conduit, means defining an outlet connected to atmosphere and said chamber, a pressure responsive exhaust valve in said atmospheric outlet movable between open and closed positions in accordance with variations in a pressure within said rigid chamber, a loading Weight secured to the free end of the bellows for causing the bellows to expand when gas is released therefrom whereby a negative pressure is created therein, said exhaust valve member being biased towards a closed position for closing said atmospheric outlet from said rigid chamber, a pressure responsive member,

References Cited in the file of this patent UNITED STATES PATENTS 2,766,753 Koch Oct. 16, 1956 2,880,719 Andreasen Apr. 7, 1959 2,969,789 Morch Jan. 31, 1961 FOREIGN PATENTS 695,586 Great Britain Aug. 12, 1953 

